1. Field of the Invention
This invention relates to the field of radiography and specifically to an improved silver halide film element useful therein. More specifically, this invention relates to radiographic film elements exposed in conjunction with intensifying screens and to an improved system which employs the techniques of computer and film enhancement of images produced thereby.
2. Background Art
The use of computer enhancement of photographic images is widely known and used in the field of space research, for example. Here, pictures transmitted to earth from outer space are enhanced with the aid of a computer and the image reconstructed to reproduce the detail distorted by the transmission thereof. Many attempts have been made to use this process in the field of radiography, i.e., medical X-ray.
In the field of radiography, it is common practice to employ light emanating from X-ray intensifying screens to expose photographic silver halide film employed therewith. The X-ray exposure source excites the phosphor in the screen which then emits light to which the silver halide film is sensitive. Radiologists require a sufficiently high-gradient medical X-ray film to obtain good visibility of subtle image detail. Because there is only a limited range of optical densities useful for radiographic diagnosis, the requirement of medium to high film contrast limits the exposure latitude to such an extent that important information is frequently lost in the toe or shoulder of the film response.
It was thought that electronic imaging techniques which would digitize X-ray images from conventional films and attempt to computer-enhance these images would be able to provide diagnostic information over a much wider range of exposures than could be achieved with conventional medical X-ray film. However, such electronic imaging techniques have not been widely used due to many factors. The image processing appeared to reduce the overall visibility of the image and radiologists were afraid to trust the results. The conversion of the photographic information to digital information that could be handled by the computer increased the so-called noise of the entire system and it was suspected that clinical information would be lost. All of these prior art systems of electronic imaging employed conventional film/screen combinations designed for use in a conventional radiological system, one wherein the developed image is examined visually directly from the film. But there are a host of film/screen systems each designed for a specific purpose. For example, high contrast films are needed for the examination of anatomical components such as bone while films with lower contrast are needed for the examination of soft tissue. Film/screen speeds also vary depending on the exposure desired. Thus, it could be seen that conventional systems are not adaptable to computer enhancement.